Hemming, S.

English

NARCIS 

Requirements of plastic films for greenhouse application : latest development in research

Wageningen Yield 

1/22/2009
1
Requirements of Plastic Films for 
greenhouse application –
Latest Development in Research 
6th European Additives & Colors Conference, 11/12 March 2009, Antwerpen
Silke Hemming,
Wageningen UR Greenhouse Horticulture
Requirements
? Covering materials for horticultural applications:
? High light transmission
? Optimum light spectrum
? Optimum heat input - low heat losses
? Optimum condensation behaviour
? High mechanical resistance
? Low sensitivity to ageing (UV, temperatures, chemicals)
? Fabrication sizes
? Costs
General
General
UV 300-400 nm morphogenesis
PAR 400-700 nm photosynthesis, morphogensis
FR 700-800 nm morphogenesis
NIR 800-2500 nm increasing greenhouse temperature
FIR 2.5-100 µm heat radiation
Philips
Relevant for horitcultural applications
Solar radiation (300-2500nm), 
energy input greenhouse
Heat radiation, 
energy loss greenhouse
UV
PAR
     N
IR
Τoutside
Glob
al ra
diat
ion
Τcrop
Τinside
photosynthesis / growth
absorption
transmission 
greenhouse covering
UV
PAR
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2
photosynthesis / growth
absorption
transmission
greenhouse covering
UV
PAR
     N
IR
UV
PAR heat
Τoutside
Τcrop ⇑
Τinside ⇑
Glob
al ra
diat
ion
increasing temperature
CΟ2 ⇓
ventilation open
Light quantity
Light quantity
Light transmission <<50%
Tropics Spain 
Light quantity
Light transmission >75%
The Netherlands Spain
0.65
0.70
0.75
0.80
0.85
0.90
0.75 0.80 0.85 0.90 0.95
transmission perpendicular [%]
tra
ns
m
is
si
on
 h
em
is
ph
er
ic
al
 [%
]
Light quantity
? PAR transmission different materials
Light measurement
(b)(a)
Measure hemispherical light
1/22/2009
3
Light quality
Photosynthesis
? 400-700nm photosynthetic active radiation
? Lightreceptors: chlorophyl, carotinoids
? Plants use theoretically all colours for photosynthesis
? Most plants use red light (≈650nm) and blue light (≈ 450nm) 
more efficiently
? Plants adapt to colours during growth
Photosynthesis
Sensitivity of 
human eye
= visible light 380-780nm
Sensitivity of
‘all’ plants
= PAR 400-700nm
Morphogenesis
? 300-800nm
? Specific lightreceptors for UVB, UVA, Blue and 
Red:Far-red
? Elongation
? Side shoots
? Leaf area and leaf thickness
? Flowering
? Colour of flowers and leaves
? Germination
Light quality
? UV-transparent films influence:
? Hardening of crops; 
? Leaf and flower colour (lettuce “lollo rosso”, aubergines, 
some flowers or flowering potplants);
? Compact growth (bedding plants, some potplants) 
? Behaviour of insects (white fly, trips, louse, (bumble-) bee)
? Population growth of insects on chrysanthemum under different UV-transparant covers
? Reproductiontest of insects on leaves ? indirect influence of UV (plant as food source)
Light quality – UV influence on insects 
after 6 weeks         louse white fly trips
#          mean         s.d              #         mean   s.d #       mean      s.d.
# 
la
rv
es
Many other influence factors: 
• temperature / humidity / light 
• sanitation
• plant vitality
glass            PMMA            PC
1/22/2009
4
Light quality
? UV transmission of different materials
0
10
20
30
40
50
60
70
80
90
100
300 320 340 360 380 400 420 440 460 480 500 520
wavelength  [nm]
tr
an
sm
is
si
on
 [%
]
PE film with UV
glass
PE film traditional
PE film with UV-blok
UVB
80
UVA Light diffusion
Light diffusion
50% 0%
Haze
Greenhouse covering materials are able to scatter light rays, 
transforming direct light into diffuse light
Light diffusion
? Vertical light distribution 
? Most light intercepted by upper leaves
? Lower leaves contribute less to photosynthesis
Ho izontal light distribution 
Ca t shadow f om greenhous  construction elements
No uniform gr wth and devel pment in gr enhouse
Background – light interception Background - photosynthesis
1/22/2009
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Background - yield
more fruits
9.2% 
6.5% 
-
Yield cucumber 2008
74% haze
27% haze
0% haze
Materials – haze and light transmission
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Horticultural glass
ETFE film
ETFE film diffuse
EVA film
EVA film diffuse
haze [-]
5 55 6 65 7 75 8 85 9 5
i l l l
hemispherical transmission [-]
Light Diffusing Covering Materials
y = 0.1145x + 0.0647
R2 = 0.8583
0.00
0.05
0.10
0.15
0.20
0.0 0.2 0.4 0.6 0.8 1.0
haze [-]
p-
h
Be careful with light losses at high haze factors
Heat input
photosynthesis / growth
absorption
UV
PAR
     N
IR
UV
PAR
he
at
Τoutside
Τcrop ↓
Τinside ↓
Glob
al ra
diat
ion
Vents can be kept closed
for a longer period
Reflection by NIR-filter
transmission 
greenhouse covering CΟ2 ⇑
NIR-reflecting inside screen (800-1100 nm)
• Screen: 40% reflection of NIR energy
• Crop: 45% reflectio of NIR radiation
• Installation parallel to roof
Greenhouse climate control:
• Temperature
• Artificial lighting (100 micro mol m-2 s-1)
• CO2 injection (1000ppm)
Experiment: inside NIR reflecting screen
1/22/2009
6
Results: ventilation opening
0
25
50
75
6 10 14 18 22
Local time (hours)
N
-V
en
t o
pe
n 
(%
)
0
3
6
9
S-
ve
nt
 o
pe
n 
(%
)
NIR N-vent REF N-vent
NIR S-vent REF S-vent
Results: crop ranspiration
Transpiration VS global 
radiation outside
NIR VS REF transpiration
NIR = 0.88*REF
0
150
300
450
0 150 300 450
REF (g m-2 h-1)
N
IR
 (g
 m
-2
 h
-1
)
NIR = 0.28x + 17.3
REF = 0.30x + 20.7
0
150
300
450
0 200 400 600 800 1000
Global radiation (W m -2)
Tr
an
sp
ira
tio
n 
(g
 m
 -2  
h 
-1
) NIR REF
Results: crop development
20
22
24
26
28
6 10 14 18 22
Local time (hours)
Tp
la
nt
 (o
C
) NIR Tp REF Tp
Slower crop development in NIR due to lower temperature in NIR
NIR-filtering
? Northern Europe: 
? Adaptable NIR-filtering screen 
outside (!) with high light transmission
? In “closed greenhouse” NIR-filtering 
reduces cooling capacity up to 30%
Foto Ecofys
NIR-filtering
? Mediterranean Countries: 
In (unheated) greenhouses use of an 
(adaptable) NIR-filtering outside screen 
only in hot periods
? Tropical regions: 
NIR-filtering coverings reduce air and 
crop temperatures permanently
Foto Ecofys
Questions?


Requirements of plastic films for greenhouse application : latest development in research

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